Collector for sulfide ores

ABSTRACT

A method for the flotation of sulfide ores is disclosed. The method comprises contacting the sulfide ores with a composition comprising at least one compound of the formula 
                         
where
     R 1 , R 2  and R 3  independently of one another are alkyl groups having 1 to 18 carbon atoms, alkenyl groups having 2 to 18 carbon atoms, aryl groups having 6 to 10 carbon atoms, or alkylaryl groups having 7 to 10 carbon atoms. Also disclosed is the process for preparing the above compound.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 10/523,746, filed Feb. 3, 2005 now U.S. Pat. No. 7,104,404,which is hereby incorporated by reference.

The present invention relates to the use of alkylamidothiophosphoric acid dialkyl esters in the dressing of sulfide ores by flotation, and to a process for preparation thereof.

In the production of sulfide ores and copper/molybdenum ores by flotation, use is made commercially of various collector types, such as dithiophosphates, xanthates, xanthogen formates and thionocarbamates (Schubert: Aufbereitung fester mineralischer Rohstoffe [Dressing of solid mineral raw materials], volume 11, 1977, pp. 298 ff.) and mixtures thereof. In combination with frothers. The flotation process separates the copper and molybdenum sulfides from gangue minerals.

Collectors cause wetting of the surface of the mineral of value which leads to the particles being rendered hydrophobic. By injecting air into the aqueous flotation pulp, air bubbles are produced, to which the ore particles which have been rendered hydrophobic have a high affinity and are discharged by the air bubbles to the surface of the flotation pulp, while gangue minerals remain in the pulp. Commercially conventional frothers include, for example, alcohols, propylene glycols and also their ethers and MIBC (methyl isobutyl carbinol).

U.S. Pat. No. 4,699,711 discloses a process for the flotation of sulfide minerals using preferably short-chain alkyl-substituted thionocarbamates.

WO 02/38277 discloses the use of mixtures of thionocarbamates and mercaptobenzothiazoles as collectors for the flotation of sulfide ores, in particular copper ore which is associated with molybdenum and gold.

Klee, F. C., Kirch, E. R., J. Pharm. Sci., 51, 1962, 423-427 discloses a process for preparing alkylamidothiophosphoric acid dialkyl esters by reacting PCl₂SN(C₂H₄) with NaOIBu in absolute diethyl ether with the addition of sodium or potassium metal.

It was an object of the present invention to find an improved collector type for sulfidic copper and copper/molybdenum ores which has better flotation results than collectors of the prior art.

It has been found that alkylamidothiophosphoric acid dialkyl esters, in particular ethylamidothiophosphoric acid diisobutyl ester, give a markedly higher recovery for the same copper/molybdenum content. The object of the present invention was in addition to find an improved process for preparing alkylamidothiophosphoric acid dialkyl esters. It should start in particular from more readily accessible starting materials and succeed without absolute solvent and without alkali metals.

The invention thus relates to a composition for the flotation of sulfide ores comprising at least one compound of the formula

where

-   R¹, R² and R³ independently of one another are alkyl groups having 1     to 18 carbon atoms, alkenyl groups having 2 to 18 carbon atoms, aryl     groups having 6 to 10 carbon atoms, or alkylaryl groups having 7 to     10 carbon atoms, and -   R⁴ is hydrogen or alkyl groups having 1 to 18 carbon atoms, alkenyl     groups having 2 to 18 carbon atoms, aryl groups having 6 to 10     carbon atoms, or alkylaryl groups having 7 to 10 carbon atoms.

The invention further relates to a process for preparing compounds of the formula

where

-   R¹, R² and R³ independently of one another are alkyl groups having 1     to 18 carbon atoms, alkenyl groups having 2 to 18 carbon atoms, aryl     groups having 6 to 10 carbon atoms, or alkylaryl groups having 7 to     10 carbon atoms, and -   R⁴ is hydrogen or alkyl groups having 1 to 18 carbon atoms, alkenyl     groups having 2 to 18 carbon atoms, aryl groups having 6 to 10     carbon atoms, or alkylaryl groups having 7 to 10 carbon atoms, which     comprises -   a) reacting a dithiophosphate of the formula (R¹O)(R²O)PS₂Me, where     Me is a cation, with an oxidizing agent in acidic solution and then -   b) reacting the resultant product with an amine of the formula     HNR³R⁴.

The invention further relates to the use of the inventive flotation reagent for the flotation of sulfide ores. The sulfide ores are preferably copper ores.

The invention further relates to a process for the flotation of sulfide ores by bringing the inventive flotation reagent into contact with the sulfide ores.

With the inventive flotation reagent, improved results for selectivity and yield can be achieved compared with standard collectors in the flotation of nonferrous metal sulfides.

Preferably, R¹, R², R³ and R⁴ independently of one another are alkyl or alkenyl groups having 1 to 10 carbon atoms. For example. R¹, R² and R³ independently of one another are C₂-C₄-alkyl groups. Particularly preferably, R¹ and R² are a butyl group, in particular an isobutyl group. R³ is in particular an ethyl group. R⁴ is in particular hydrogen.

Me is preferably an alkali metal, alkaline earth metal, ammonium ion or hydrogen ion, in particular Na or K.

As oxidizing agent, use can be made of any able to oxidize dithiophosphate, for example a chlorite, for instance sodium chlorite; hypochlorite or chlorate.

As acid, use can be made of any compound which releases hydrogen ions in aqueous solution. Preferably, this relates to mineral acids, for example sulfuric acid, nitric acid, phosphoric acid or hydrochloric acid. If appropriate, the acid can be an oxidizing acid which simultaneously acts as oxidizing agent.

Preferred dithiophosphates are diisobutyl dithiophosphate, diethyl dithiophosphate, diisopropyl dithiophosphate, di-sec-butyl dithiophosphate and diamyl dithiophosphate.

Flotation can be applied to all metal sulfides (apart from Fe), with Cu, Mo, Pb, Zn, and Ni being particularly preferred. Particularly good results are to be observed in the dressing of Cu and Mo. The inventive flotation reagent can be used in a broad pH range (2 to 12) and is added to the aqueous pulp at a concentration between, preferably, 0.001 and 1.0 kg/tonne of crude ore.

The inventive flotation reagent achieves significant improvement of recovery and selectivity compared with the xanthogen formates and thionocarbamates of the prior art. Examples 1, 3 and 5 clearly show that the recovery of copper and molybdenum is higher than with the corresponding standard reagent. Example 3 is to be emphasized, in which, with 77.3% copper recovery and 69.5% molybdenum recovery, values significantly higher by 4.8 and 7.1% are achieved than with the corresponding amount of ethyl isopropyl thionocarbamate {example 4(V)}, where the copper or molybdenum content remains at the same level.

EXAMPLES A) Preparation of Ethylamidothiophosphoric acid Diisobutyl Ester

Stage 1 (Oxidation): 4(RO)₂PS₂Na+NaClO₂+2H₂SO₄→2(RO)₂PSS—SSP(OR)₂+NaCl+H₂O+2Na₂SO₄ R=C₄Hg-isobutyl Stage 2 amidation: (RO)₂PS—S—S—SP(OR)₂+2H₂NCH₂CH₃→2(RO)₂PSNHR_((aq))+H₂S₂(liq aq)  2a) H₂S₂+H₂NR→(RNH₃)HS₂(liq aq)  2b)

To prepare ethylamidothiophosphoric acid diisobutyl ester, 1670 g (3.17 mol) of a 50% strength solution of sodium diisobutyldithiophosphate were homogenized with 725 g of a 22% strength sodium chlorite solution (1.76 mol) for 5 min. 346 g of a 50% strength sulfuric acid were added slowly over 2-3 h with constant stirring, the temperature of the reaction mixture being kept between 40 and 50° C. The mixture was stirred for a further 30 min and the reaction mixture was then cooled to 30-40° C. After separation of the phases, the organic phase (approximately 778 g) was decanted and reacted with 250 g of a 70% strength ethylamine solution which had been added slowly over approximately 2-3 h. The temperature was kept at 40-60° C. by cooling (exothermic reaction). The reaction mixture was then heated under reflux at 70-80° C. for approximately 3 h.

The reaction mixture was cooled to 40-50° C. with stirring, and 441 g of diethylene glycol were added. After a further 30 min, the mixture was cooled to 20-25° C. The concentration of the reaction product was set at the desired active ingredient content using 95 g of water.

After filtration 1551 g of a transparent reddish-oily solution of the product were obtained.

B) Action as Collector

The following collector/frother combinations were used:

TABLE 1 Collector/frother combinations Example No. Composition 1 Collector: ethylamidothiophosphoric acid diisobutyl ester (27 g/t) Frother: oxo residue/polypropylene glycol methyl ether, MW = 400 g/mol (5:1, 15 g/t) 2 Collector: ethyl isopropyl xenthogen formate (27 g/t) (control) Frother: oxo residue/polypropylene glycol methyl ether, MW = 400 g/mol (5:1, 15 g/t) 3 Collector: ethylamidothiophosphoric acid diisobutyl ester (6 g/t) Frother: oxo residue/polypropylene glycol, MW = 425 g/mol (20 g/t) 4 Collector: ethyl isopropyl thionocarbamate (6 g/t) (control) Frother: propylene glycol methyl ether, MW = 250 g/mol/ MIBC (1:1, 28 g/t) 5 Collector: ethylamidothiophosphoric acid diisobutyl ester (33 g/t) Frother: oxo residue/polypropylene glycol, MW = 425 g/mol (40 g/t) 6 Collector: ethyl isopropyl xanthogen formate (33 g/t) (control) Frother: oxo residue/pine oil (6:4, 40 g/t) Oxo residues here have roughly the following composition: Concentration range Constituent (% by weight) di-2-ethylhexyl ether 10-25  2-ethylhexanoic acid 2-ethylhexyl ester 10-25  C₁₆ lactones 4-20 2-ethylhexyl butyrate 3-10 2-ethylhexane-1,3-diol mono-n-butyrate 5-15 2-ethylhexanol 4-10 C₄- to C₈-acetals 2-10 2-ethylhexane-1,3-diol 2-5  ethers and esters ≧ C₂₀ 0-20

TABLE 2 Results of the flotation experiments Feed Concentrate Cu Mo Cu Mo Example content content content content Recovery Recovery No. in % in % in % in % in % in % 1 1.13 0.03 11.4 0.25 92.1 80.3 2 11.5 0.23 91.2 76.9 (control) 3 0.62 0.017 4.1 0.14 77.3 69.5 4 4.3 0.15 72.5 62.4 (control) 5 0.83 — 10.3 — 89.2 — 6 10.2 — 86.7 — (control) 

1. A process for preparing compounds of the formula

where R¹, R² and R³ independently of one another are selected from the group consisting of alkyl groups having 1 to 18 carbon atoms, alkenyl groups having 2 to 18 carbon atoms, aryl groups having 6 to 10 carbon atoms, alkylaryl groups having 7 to 10 carbon atoms, and mixtures thereof, and R⁴ is hydrogen or selected from the group consisting of alkyl groups having 1 to 18 carbon atoms, alkenyl groups having 2 to 18 carbon atoms, aryl groups having 6 to 10 carbon atoms, alkylaryl groups having 7 to 10 carbon atoms, and mixtures thereof, said process comprising a) reacting a dithiophosphate of the formula (R¹O)(R²O)PS2Me, where Me is a cation, with an oxidizing agent in acidic solution and then b) reacting the resultant product with an amine of the formula HNR³R⁴.
 2. The process as claimed in claim 1, wherein R¹, R² and R³ independently of one another are C2-C4-alkyl groups.
 3. The process as claimed in claim 2, wherein R¹ and R² are a butyl group, R³ is an ethyl group and R⁴ is hydrogen.
 4. The process as claimed in claim 3, wherein R¹ and R² are an isobutyl group. 